1. Technical Field
The present disclosure relates to a hydraulic brake system, and more particularly, to a hydraulic brake system capable of reducing pressure pulsation caused by operation of a piston.
2. Description of the Related Art
A vehicle is necessarily fitted with a brake system. Recently, various kinds of brake systems have been suggested to obtain stronger and more stable braking force. Such brake systems include an anti-lock brake system (ABS) that prevents slippage of a wheel during braking, a brake traction control system (BTCS) that prevents slippage of a driven wheel upon rapid start or rapid acceleration of a vehicle, a vehicle dynamic control system (VDC) that is a combination of the anti-lock brake and traction control systems and maintains a stable driving state of a vehicle by controlling pressure of a brake liquid, etc.
Such a hydraulic brake system includes a master cylinder for generating a desired pressure for braking, a plurality of solenoid valves for controlling braking hydraulic pressure transmitted to wheel brakes of a vehicle, a low pressure accumulator for temporarily storing oil, a hydraulic motor and pumps for pumping out the oil temporarily stored in the low pressure accumulator, orifices for reducing pressure pulsation of the oil pumped by the pumps, an electronic control unit (ECU) for electrically controlling the solenoid valves and the pumps, and the like. Further, a valve assembly of the solenoid valves, the accumulator, the pumps, the hydraulic motor, and the like are compactly installed in an aluminum hydraulic block (modulator block). The ECU is connected to the hydraulic block and includes an ECU housing which receives a coil assembly of the solenoid valves and a circuit board.
In the hydraulic brake system described above, although the orifice disposed near an outlet port of each pump reduces pressure pulsation caused by operation of the pump in a process of multiplying braking pressure, there is difficulty achieving complete reduction of the pressure pulsation since the orifice is provided to control a cross-sectional area of a flow passage for the purpose of damping reduction.
Further, pressure pulsation may be reduced by increasing the number of pistons of the pump. In this case, however, there is a problem of increase in manufacturing costs through increase of the weight and volume of the motor for improving performance of the motor. Moreover, the peak of pressure pulsation continuously generated due to operation of the pump can act as a source of noise of the hydraulic brake system.